
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    a {
      text-decoration: none;
    }

    input,
    button {
      background: transparent;
      border: 0;
      outline: none;
    }

    body {
      height: 100vh;
      background: linear-gradient(#141e30, #243b55);
      display: flex;
      justify-content: center;
      align-items: center;
      font-size: 16px;
      color: #03e9f4;
    }

    .loginBox {
      width: 400px;
      height: 364px;
      background-color: #0c1622;
      margin: 100px auto;
      border-radius: 10px;
      box-shadow: 0 15px 25px 0 rgba(0, 0, 0, .6);
      padding: 40px;
      box-sizing: border-box;
    }

    h2 {
      text-align: center;
      color: aliceblue;
      margin-bottom: 30px;
      font-family: 'Courier New', Courier, monospace;
    }

    .item {
      height: 45px;
      border-bottom: 1px solid #fff;
      margin-bottom: 40px;
      position: relative;
    }

    .item input {
      width: 100%;
      height: 100%;
      color: #fff;
      padding-top: 20px;
      box-sizing: border-box;
    }

    .item input:focus+label,
    .item input:valid+label {
      top: 0px;
      font-size: 2px;
    }

    .item label {
      position: absolute;
      left: 0;
      top: 12px;
      transition: all 0.5s linear;
    }

    .btn {
      padding: 10px 20px;
      margin-top: 30px;
      color: #03e9f4;
      position: relative;
      overflow: hidden;
      text-transform: uppercase;
      letter-spacing: 2px;
      left: 35%;
    }

    .btn:hover {
      border-radius: 5px;
      color: #fff;
      background: #03e9f4;
      box-shadow: 0 0 5px 0 #03e9f4,
        0 0 25px 0 #03e9f4,
        0 0 50px 0 #03e9f4,
        0 0 100px 0 #03e9f4;
      transition: all 1s linear;
    }

    .btn>span {
      position: absolute;
    }

    .btn>span:nth-child(1) {
      width: 100%;
      height: 2px;
      background: -webkit-linear-gradient(left, transparent, #03e9f4);
      left: -100%;
      top: 0px;
      animation: line1 1s linear infinite;
    }

    @keyframes line1 {

      50%,
      100% {
        left: 100%;
      }
    }

    .btn>span:nth-child(2) {
      width: 2px;
      height: 100%;
      background: -webkit-linear-gradient(top, transparent, #03e9f4);
      right: 0px;
      top: -100%;
      animation: line2 1s 0.25s linear infinite;
    }

    @keyframes line2 {

      50%,
      100% {
        top: 100%;
      }
    }

    .btn>span:nth-child(3) {
      width: 100%;
      height: 2px;
      background: -webkit-linear-gradient(left, #03e9f4, transparent);
      left: 100%;
      bottom: 0px;
      animation: line3 1s 0.75s linear infinite;
    }

    @keyframes line3 {

      50%,
      100% {
        left: -100%;
      }
    }

    .btn>span:nth-child(4) {
      width: 2px;
      height: 100%;
      background: -webkit-linear-gradient(top, transparent, #03e9f4);
      left: 0px;
      top: 100%;
      animation: line4 1s 1s linear infinite;
    }

    @keyframes line4 {

      50%,
      100% {
        top: -100%;
      }
    }
</style>
</head>

<body>
  <div class="loginBox">
    <h2>login</h2>
    <form action="">
      <div class="item">
        <input type="text" required>
        <label for="">userName</label>
      </div>
      <div class="item">
        <input type="password" required>
        <label for="">password</label>
      </div>
      <button class="btn">submit
        <span></span>
        <span></span>
        <span></span>
        <span></span>
      </button>
    </form>
  </div>
</body>
</html>